Electrons flowing over rough terrain exhibit elaborate folds and caustics (lines where one space ends and another begins) made to appear here as thin sheets of folded translucent kelp, which in fact show the same universal caustic structures.

Electrons injected at one point contact, the “sun,” flow in a wire riddled with random imperfections. The quantum aspect of the electrons is shown in color: we follow the wave nature of the electrons by assigning red to the crest of the wave, cyan to a trough, continuously around the color circle.

Electron tracks in a nano device, with electrons launched at various places and followed for a short time. Individual electron tracks are visible, and it can be seen how they gather to make caustics after their launch in a narrow range of angles.

Electron tracks in a nano device, with electrons launched at various places and followed for a short time. Individual electron tracks are visible, and it can be seen how they gather to make caustics after their launch in a narrow range of angles.